Glass spandrel panels have been used architecturally for many years as the outer surface of buildings between the floors, which must be opaque, and which must exhibit the same color as the windows of the floors both above and below when viewed in reflected light. For many years this was accomplished by use of ceramic colors fused to the inside surface of the glass sheet. For insulation purposes, an insulation board made from fiberglass, other fibrous materials, or sheets of polyurethane foam were fixed to the inner surface of the glass. Any number of adhesives can be used for securing these insulation boards to the colored enamel surface without adversely effecting the color as viewed in reflected light from the opposite side when installed.
More recently, however, these glass spandrels have utilized a metallic coating comprising a thin film of gold, aluminum, chromium or other metals applied to the inner surface of the glass in preference to the ceramic colors previously fused to the inside surface of the glass. These thin metallic films, as is well known, are applied by vacuum deposition or sputtering. These metallic films are extremely thin and fragile being on the order of from about 200 to 500 angstroms in thickness. They are transparent and transmit light and appear opaque in reflected light, as such, they are frequently used for solar control while providing a mirror-like metallic finish to the glass. Such glass spandrels are becoming widely used in insulated glass windows usually being assembled with a sheet of clear glass inside of and spaced from the metal film coated glass sheet with an air space therebetween and a suitable sealing component around the periphery of the two sheets of glass. When it is desired, as is usually the case, to retain the same color in the opaque areas of the building such as between floors as the colors in the windows in the floors above and below, it is necessary to provide for insulating the opaque panels in order to minimize heat loss. However, when attempts were made to bond the insulation board directly to the metallic coatings in a manner similar to that previously used with the fused ceramic colors, it was found that the fragile metallic coatings were easily penetrated by the fibers or surface texture of the insulation board. Further, these metallic films were so thin that they provided little if any hiding power and every spot of adhesive used to secure the insulation board could be seen through the glass. This "show through" was only one of the problems, for the solvents and other ingredients in the adhesives tended to deleteriously effect the fragile metallic films by corrosion or other undesirable reaction.
Accordingly, in order to provide architectural structures with the same reflected color in the opaque areas of the building, as in the windowed areas of the building, it was necessary to support the insulation board independently behind the metallic coated glass by means of a separate frame and air space, or alternately, to substitute a piece of metallic sheet metal for the sheet of clear glass used in the sealed window units. Both of these alternatives are exceedingly expensive.